Comparison of intravenous and endobronchial atropine: a pharmacokinetic and -dynamic study in pigs

In an experimental animal study using adolescent pigs we compared the pharmacokinetics and -dynamics of atropine following intravenous injection (0.25 mg, n = 6) or endobronchial instillation (2 mg, n = 6). Results showed that endobronchial atropine is rapidly absorbed by the pulmonary circulation, resulting in a peak plasma concentration of 48.8 +/- 25.9 ng ml-1 (mean +/- SD) after 2 min, compared to 46.3 +/- 16.7 ng ml-1 in the first min after intravenous injection. A first increase in heart rate could be observed within 1 min after both routes of drug administration. Significant changes in heart rate were found 9-30 min after endobronchial and 12-15 min after intravenous medication, with a maximum after 9 min (+57%) and 12 min (+24%), respectively. Mean bioavailability of atropine following the endobronchial route reached only 23% during the first 6 h when compared to intravenous administration. In light of this reduced bioavailability, we suggest an adult dosage in humans of atropine 2 mg diluted in 5-10 ml of saline administered endobronchially to attain a reliable increase in heart rate during a cardiac emergency when, in an intubated individual, no intravenous line is readily available.